The present invention relates to automatic machines, and particularly to automatic machines to the type having moving parts which have more than one degree of freedom and which can be controlled by actuators to perform different movements in accordance with a program stored in a memory of the machine. In one type of such machine the program is fed into the memory by manually displacing the moving parts through the required path to generate, by means of position transducers connected to the parts, signals representing the movements, which signals are recorded in some way in the memory and subsequently used to control the actuators.
One known type of such automatic machine has an articulated mechanical arm movable with several degrees of freedom by a number of actuators. The arm is connected to position transducers the outputs of which feed a memorizing and processing device which can control the actuators. An automatic machine of this type is usually referred to as a "robot".
Known methods for controlling such "robots" comprise a learning stage in which the operator moves the free end of the arm through the required path so as to generate in the position transducers electrical signals in the form of sequential numerical data representing in quantized form the spatial co-ordinates of the sequence of points which constitute the path of the free end of the arm in space, this data being memorized in the memory. The memorized data can then be used to control the actuators to move the arm so that it reproduces the movement it has been "taught" by the initial manual movement. Normally, because of the large amount of information which may be contained in the sequential numerical data representing the movement of the arm, a high capacity memory means, such as, for example, a magnetic tape, is used as the memory.
However, where such a memory is required to be read a large number of times in order to control the robot to repeat its movement a large number of times, there is the disadvantage of heavy wear of the magnetic tape, and this inevitably involves alteration of some of the memorized information, leading to a reduction in the reliability of faithful reproduction of the required path by the free end of the mechanical arm of the robot. The use of more reliable means of memorization, such as magnetic discs, is not convenient from the point of view of economy because of the large amount of information to be recorded in order to represent exactly the path of the arm.